As explained in Debian bug #826727, the problem is that “QtWebKit was removed from the Qt4 in Debian. There is no fix other than a Qt5 port of anki.”

Fortunately, that’s not the only solution, from the perspective of Anki users. The Anki web site gives us a clue, but it’s not very complete, so these instructions should get you all of the way there.

Download a working version of python-qt4. The version number is particularly important. I found that 4.11.4+dfsg-1 works for me, whereas 4.11.4+dfsg-2 does not! I also downloaded the matching version of python-qt4-sql. If you have other python packages installed that depend on a properly matching version, look for them here.